At eight years older than that fellow who needs to be fed in “When I’m Sixty-Four,” Paul McCartney is not supposed to be able to do what he’s been doing, such as Wednesday night at the United Center. There’s little precedent for a 72-year-old rocker putting on almost-three-hour shows that can be evaluated without an asterisk—i.e., some sort of disclaimer that it’s not bad for a senior citizen.

About the only comparison is the Rolling Stones, with Mick Jagger (ageless energy) and Keith Richards (not so ageless energy) recently having turned 70 and drummer Charlie Watts, the band's still-crackling engine, now 73 — but they don't play quite as long or as often as McCartney, and they've gotten creaky around the edges. Bob Dylan also is a year older that McCartney, but he sounds like he’s been gargling battery acid and is far from the showman that the former Beatle remains.

It’s true that McCartney no longer boasts the pure, clear tone of his early days, and he can get pinched trying to hit high notes—even as his falsetto, such as on “Here Today,” remains stunning — yet he holds little back. He still screams “Helter Skelter,” the hardest song in his catalog, and gives “Maybe I’m Amazed” a soulful belting, his straining to hit each of those vocal peaks only adding drama and passion.

And when he starts to sing “Hey Jude” or the “Once there was a way…” beginning to “Golden Slumbers,” he’s so unmistakably Paul that you may suddenly feel a giant lump in your throat. He is, after all, the living songwriter-performer who has done the most to shape popular music — and in many ways the culture surrounding it. Some guy behind me at the United Center kept shouting, “Thank you! Thank you!” at McCartney, and while one part of me wished he’d put a sock in it, another part completely got it.

McCartney’s hospitalization for a viral infection, which prompted him to cancel all five of his Asian concerts in May and to reschedule seven U.S. concerts from June to October, served as a reminder that he, like anyone else, is vulnerable. How long can he keep doing this?

When drummer Abe Laboriel, Jr. doubled McCartney's lead vocals on the first two songs, "Eight Days a Week" and "Save Us," I wondered whether McCartney's voice hadn't fully recovered. But after some early shakiness, it found its comfort zone, whether loud ("Maybe I'm Amazed") or soft ("And I Love Her," "Blackbird").

And as has been his practice for the past several years, he performed for about two-and-a-quarter hours before the first encore without appearing to take a sip of water. He’s one of the wonders of the artistic world, a thoroughly joyous presence, and these moments must be savored. The rest is just details.

Then again, I like details:

Number of songs he played Wednesday: 39 (with the concluding “Golden Slumbers”/“Carry That Weight”/”The End” medley counted as three, as on “Abbey Road”)

Number of Wednesday’s songs that he also played in Milwaukee’s Miller Park last July: 35. They were pretty much in the same order too.

Number of Wednesday’s songs that he also played over two nights at Wrigley Field in 2011: 26. He told a lot of the same stories too: Jimi Hendrix playing “Sgt. Pepper’s Lonely Hearts Club Band” in concert and asking Eric Clapton to tune his guitar; McCartney writing “Blackbird” as a nod to the Civil Rights movement and appreciating people who told him they tried to learn it on guitar; McCartney playing George Harrison a ukulele version of “Something”; the Russian defense minister telling McCartney the first record he ever bought was “Love Me Do”…

McCartney acknowledged that many in the audience might have heard the Hendrix anecdote before, and he introduced another by saying, “One of the stories I tell in concert is…” You could feel routine creeping into this set. But the laugh lines still landed.

Number of songs he played from “New,” his album from last year: 4. (These were the four songs he didn’t play in Milwaukee.) Give the guy credit that he’s willing to support his new/“New” material — and it held its own. The title track is as joyous a piece of pop as he’s confected in decades (it made sense replacing “Your Mother Should Know” in the set), the piano-driven “Queenie Eye” and guitar-strumming “Everybody Out There” built up decent heads of steam — though neither triggered the kind of call-and-response no doubt envisioned by their composer — and “Save Us” is a throwaway rocker that at least injected energy, though it's no "Junior's Farm" or "Jet."

McCartney made a funny-sharp observation that he can feel when a new song is going over well, yet "when you do the old songs, you see all the phones come out."

Number of songs he performed that were released between 1982 (“Here Today”) and 2012 (“My Valentine”): 0. Given the numerous worthy albums and songs he released over that 30-year stretch, it’s a shame he doesn’t make the case for any of this material in concert the way that, say, former collaborator Elvis Costello revisits different phases of his career when playing live. This gets to the crux of a central tension with McCartney: the desire to please vs. the desire to get creative.

His albums are almost always weirder than advertised; “New” is all over the map stylistically and mostly successful, and his 2008 The Fireman collaboration with producer Youth (“Electric Arguments”) is truly out there. Yet you get the feeling he’s thinking that the people paying hundreds of dollars to see him aren’t expecting a deep catalog exploration, and that's too bad, because McCartney’s catalog is as deep as anyone's, so there are even a lot of hits he never plays.

The taped pre-concert music included funky remixes of such songs as “No More Lonely Nights,” “Goodnight Tonight” and “Silly Love Songs,” the first of which he has yet to perform live while the other two haven’t appeared in a McCartney set since he disbanded Wings. What he does play doesn’t get reinterpreted; he seems intent on triggering concertgoers’ memories of the original recordings even to the point of having keyboardist Paul “Wix” Wickens replicate the string parts of “The Long and Winding Road” that producer Phil Spector had added over McCartney’s objections. (At least there’s no live choir.)

Why not do the superior, streamlined "Let It Be...Naked" arrangement? Why, for that matter, not play "Yesterday" solo instead of having Wix lather on more synthesized strings? You're Paul McCartney; you can perform the songs as you think best and toy with the arrangements when so inspired. The audience will stick with you and might appreciate the occasional surprise.

Side note: Many people at the United Center were sitting during “The Long and Winding Road,” yet everyone stood when “Maybe I’m Amazed” began, indicating how high the latter solo McCartney power ballad has risen.

The song McCartney has played most in concert: “Let It Be,” Wednesday’s performance of which was McCartney’s 498th since he launched his post-Wings career, according to the website Setlist.fm. Runners-up are “Hey Jude” (491) and “Band on the Run” (481), though if you added the Wings performances of “Band on the Run,” it might rise to the top.

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